Dynamo-electric machine regulation



July 10, 1934. w. H. POWELL DYNAMO ELECTRIC MACHINE REGULATION Filed Feb. 27, 1931 Patented July 10, 1934 UNITED STATES PATENT OFFICE DYNAMO ELECTRIC MACHINE REGULATION Application February 27, 1931, Serial No. 518,698

14 Claims.

This invention relates in general to dynamoelectric machine regulation, and it is more particularly concerned with the provision of simple and efiicient means for effecting regulation of 6 such machines through the intermediary of field energizing windings of the machines and securing desired results with relatively small expense in the matter of both initial installation and operation under service conditions.

10 It has been quite usual in connection with the design and operation of direct current machines provided with windings carrying current varying with the load current of the machine, such as compounding, both cumulative and differential,

and commutating and compensating windings,

and generally where the desired regulating effeet is obtainable with relatively few turns of winding, sometimes only a fraction of a single turn being necessary, to provide resistance in shunt to the winding, such resistance being of relatively low ohmic value to insure that a suit ably large proportion of the load current is shunted about the winding, thus permitting a sufiiciently small current to pass through the winding itself, by reason of which a sufiiciently great length or number of turns of winding of relatively small cross-section may be effectively utilized to secure the desired number of ampere turns for the field poles, either main or auxiliary. Particularly in larger sized machines, the amount of current that must be handled by a series shunt resistance, in order to secure the desired series effect in a winding, is very large, and the provision of a suitable series shunt resistance involves a very considerable item of the cost of the installation, and its use involves considerable losses in the operation of the machine.

The present invention contemplates utilization of a plurality of distinct windings of the series type, whether compound, either cumulative or difierential, or commutating or compensating, in such interrelation that each serves in the way of a current-diverting shunt for the other winding, while insuring the desired current fiow in each winding proportional to the armature current, with a corresponding very considerable saving in expense by reason of avoiding the usual series shunt resistances of the character that would otherwise be required and permitting the use of conductors of reduced and more or less standard cross-sectional area. With proper proportioning of the number of turns and the resistance of the several series type windings constituting the parallel branches of the circuit, it is possible to secure the desired results with considerably reduced cost of installation and with decreased losses in operation, through the avoidance of relatively large 1 R losses incident to the use of larger series shunt resistances.

Features of the present invention find especially desirable application in connection with the control of direct current motors of both the constant voltage type and also such as constitute a part of drives of the Ward-Leonard type, where the speed of the motor is controlled by or is responsive to variation in the voltage of a generator supplying energy to the armature of the motor, and one or the other of the main machines is provided with a commutating Winding and also differential series winding which exerts an aux- 7o iliary efiect on the main field of the machine as the load comes on the motor, for the ultimate purpose of insuring maintenance of the motor speed, or reducing its tendency to droop, in spite of the increased load on the motor; and, in certain cases, advantages of the invention may be realized where it is desired that the speed of the motor have a drooping characteristic in excess of normal, in which event the auxiliary series winding may have a slight cumulative, instead 30 of differential effect.

It is an object of the present invention to provide a dynamo-electric machine embodying improved regulating means including a plurality of field windings of the series type having different 35 characteristics in the operation of the machine and connected in parallel to each other in the armature circuit of the machine, each of said windings acting as a current-diverting shunt for the other winding.

It is a further object of the present invention to provide a dynamo-electric machine of the character hereinabove described, wherein a commutating field winding and an auxiliary series field winding on the machine are arranged in shunt to each other in the armature circuit of the machine.

It is a further object of the present invention to provide a motor control system of the Ward- Leonard type wherein one of the machines is provided with a plurality of series type wind ings having difierent characteristics in the operation of the machine and connected in parallel to each other, and one of said windings serving through its efiective control of the main field 5 energization of the machine, to reduce the tendency of the motor speed to droop on increase in load on the motor.

These and other objects and advantages are attained by the present invention, various novel features of which will be apparent from the description and drawing herein, disclosing an embodiment of the invention, and will be more particularly pointed out in the claims.

In the accompanying drawing, there is disclosed a Ward-Leonard system including a load motor embodying features of the present invention. This motor, indicated at 10, may be considered as one of relatively great power, such as is ordinarily used for driving a rolling mill or the like, and the armature of this motor is supplied with direct current energy by generator 12, the main field winding 13 of the motor being supplied from a separate source, such as the ex citer 14 which, along with the generator 12, may be driven by the prime mover or motor 15, here shown as an alternating current induction motor, or, if the speed of the main motor 15 is not sufiiciently high, the exciter 14 may be driven by a separate high speed prime mover or motor, preferably of the constant speed type.

The motor 15, or other power source, may also drive an auxiliary, preferably constant potential, generator 16 which supplies energy to a shunt field winding 17 on the main exciter 14; and a resistance controller 18 may be provided for varying the current in the circuit of the field winding 1'7. The auxiliary exciter 16 may have its field energized by a shunt winding 19, the circuit of the latter being provided with suitable resistance controlling means for adjusting the energizing current in the field winding 19 to the desired value.

The field of the main generator 12 is energized by a winding 20 of the shunt type, separately excited from a suitable source of variable potential, such as the exciter 21 which likewise may be driven by the main motor 15; and a suitable resistance controller may be provided in the circuit of the winding 20 for definitely adjusting the resistance of the latter circuit to the desired value. The field of the exciter 21 is energized by a winding 23 having its circuit supplied from the constant potential auxiliary exciter 16, preferably through a variable and reversible rheostat 24. It will be apparent that, through suitable adjustment of the controller 24, the resistance of the circuit of the field winding 23, and hence the potential developed at the terminals of the auxiliary exciter 21, and likewise the potential developed at the terminals of the main generator 12, may be adjusted to any desired value and reversed, in accordance with the desire for operation of the main motor 10 in a forward or reverse direction and at different operating speeds.

Machines of the character of the main generator 12 and motor 10, especially where variable voltage or speed operation is contemplated, are usually provided with commutating poles. The commutating winding of the motor 10 is indicated at 26. Such a commutating winding, particularly in the case of a motor of relatively large size, is usually of a relatively small number of turns. The main motor 10 is also provided with a differential or demagnetizing winding 27 disposed on the main field poles, this latter winding functioning, through its effect in reducing the main field of the motor in proportion to increase in load thereon, to hold up or maintain the speed of the motor at a desired value, corresponding to the setting of the field controlling rheostat 24, in the present instance, as the load on the motor increases. The number of series turns required to produce the desired demagnetizing effect and thus suitably hold up the motor speed is small and may correspond to only a fraction of a turn per pole of winding carrying the full armature current.

It often becomes dilficult to provide the desired energization effects of the commutating field or other such auxiliary series field of a machine, where the windings must be made up of a relatively small number of turns of relatively great cross-sectional area; and, accordingly, the use of series shunt resistances has been resorted to in order to insure the required energizing effects, thus permitting use of windings of reduced cross-sectional area and also facilitating suitable disposition of the required number of turns of the winding on the poles of the machine.v

Series shunt resistances of a character suitable for insuring the proper division of the current in a portion of the series circuit of a relatively large machine are extremely expensive items, for they must be of such design and construction as to safely carry relatively large amounts of current, with suitable provision for dissipating heat generated therein. Further, aside from the matter of relatively high expense of installation, such resistances involve the element of relatively great energy losses in operation.

I have conceived the idea of avoiding use of the ordinarily required series shunt resistances inconnection with series energizing windings of ,1,

the character of the differential series or demagnetizing winding 2''] and likewise, to a corresponding extent, the commutating winding 26, through utilization of the expedient of connecting the demagnetizing series winding 27 as a shunt about the commutating field Winding 26, as indicated in the drawing, the inherent effect being the required reduction in the normal current through each winding. While it is possible to design the windings 26 and 27 for shunt connection with each other, so that they are of the required dimensions to produce the desired number of ampere turns for both commutating and demagnetizing purposes, without the use of resistances in series or shunt thereto, nevertheless, in order to afford reasonable facility in the selection of winding material of standard sizes and to permit securing the desired ampere turns with whole numbers of turns of windings, and also to make correction for any inaccuracies in or departure from the desired division of the current between the several windings which carry current proportional to the load current, resistances 28 and 29 may be inserted in the immediate circuits of the commutating winding 26 and the demagnetizing winding 27, respectively; and this arrangement may be supplemented, in cases where greater refinement is desired, by resistances in shunt to one or both of the windings 26 and 27, and carrying relatively small current, thus assuring the desired proportional effects of these windings at all times. Under ordinary circumstances, where the resistances 28 and 29 in the circuit of the windings 26 and 27, respectively, are once adjusted to values dependent upon the characteristics of the particular machine, there should be little, if any, occasion for further adjustment of these resistances.

While the motor 10 may be regulated as to speed by suitable adjustment of the resistance controller 24 in the circuit of the field energizing winding 23 of the auxiliary exciter 21, we may assume that the voltage at the terminals of the generator 12 is constant and, hence, that constant voltage is supplied to the terminals of the motor 10; and under these circumstances, the speed of the motor may be varied by varying the voltage at the terminals of the winding 13, either by varying the voltage of the exciter 14 through adjustment of the field controller 18 or, with constant exciter voltage, by varying the resistance in circuit with the Winding 13, as by suitable adjustment of a resistance controller 31 in series with the field winding.

Since there is greater tendency for the motor speed to droop or vary from normal with increase in load on the motor, at the lower operating speeds thereof than its higher operating speeds, it may be desirable to likewise adjust to some extent the resistance of the shunt series circuit through the demagnetizing winding 27, especially where the range in normal operating speeds is considerable, in order to thereby insure the desired constancy of motor speed for the various definite settings of the field controller 31, as the load on the motor varies. The desired control of the current in the winding 27 to attain the desired refinement in the matter of holding up the speed of the motor as the load thereon is increased, may readily be secured through the use of an auxiliary resistance controller, such as is indicated at 32, the adjustment of which secures the desired variation in the demagnetizing efiect of this winding, corresponding to the various normal operating speeds of themotor which are determined by the adjustment of the field rheostat 31, the controller 32 being operated to reduce the resistance of the circuit of the winding 27 as the controller 31 is actuated to reduce the speed of the motor.

Particularly where it is contemplated that the variation in the energizing effect of the field winding 13 for the purpose of securing variation in the motor speed is likely to occur quite often, it may be desirable to provide for such simultaneous operation of the resistance controller 31 in the circuit of the winding 13 and the resistance controller 32 in the circuit of the demagnetizing field 27 as will insure that for each setting of the controller 31, corresponding to a particular normal motor speed, a corresponding settingof the resistance controller 32 is obtained, the result being that the demagnetizing effect of the winding 27 is always such as produces the desired character of speed-load curve of'the motor. As indicated in the drawing, the desired result along this line may be secured through mechanically connecting movable arms of the controllers 31 and 32 by means of a connecting rod 34 to thereby obtain the desired simultaneous operation of these controllers.

Under ordinary circumstances, even with considerable adjustment of the controller 32 in the circuit of the winding 2'7 to accommodate for the different settings of the controller 31 in the circuit of the field winding 13, the difference in proportions of the currents through the commutating winding 26 and the demagnetizing winding 27 connected in shunt to each other in the armature circuit of the motor, is hardly great enough to have any substantial result upon the commutating efiects secured through the winding 26 in the operation of the motor. However, in order to secure added refinement in operation of the motor, an auxiliary controller may be provided in the circuit of the winding 26, to obtain any required fine adjustment of the current in the winding 26; and, if desired, this controller may likewise be arranged for simultaneous operation with the controller 32 and the controller 31, to

thereby secure the desired current adjustment.

If, instead of controlling the speed of the motor 10 by adjustment of the resistance controller 31 in the circuit of the field winding 13, the desired speed variation is secured by varying the voltage applied to the armature terminals of the motor, by adjustment of the resistance controller 24 in the circuit of the exciting field winding of the exciter 21 for the generator 12, the movable arm of this controller 24 being moved in either direction from a mid position to vary or reverse the potential of the generator 10, then the movable arm of the controller 32 in the circuit of the demagnetizing winding 27 may be arranged for simultaneous operation with the movable arm of the controller 24. As indicated in the drawing, the desired operation of the controller 32 may be attained through the connection of the movable arm of the latter controller to the arm of the controller 24 through a sliding rod 35 which may be connected to the arm of controller 24 through a pin and cam slot connection, indicated at 36, the cam formation being such that when the arm of controller 24 is in its mid position, corresponding to minimum voltage on the generator 12 and the motor 10, the arm of controller 32 is in position to reduce the resistance of the circuit of the demagnetizing winding 27, and, as the arm of controller 24 is moved in either direction from mid position, thearm of controller 32 is moved :1. corresponding amoun; to insert the required resistance in the circuit of the Winding 27.

In certain contingencies, particularly where the motor 10 operates in parallel with another motor, as when driving a common load, it may be desirable that the motor, instead or having nearly flat speed-load characteristics, have an excessive drooping characteristic. In such event, it may be desirable that the winding 27, instead of exerting a demagneiizing effect on the field of the motor, exert a slight cumulative effeet; and provision for the exertion of such efiect may be had through the operation of a reversing switch 37 in the circuit of the winding 27, to its opposite closed position which provides for flow of current through the winding 27 in a direction opposite to that which produces the demagnetizing effect described hereinabove.

While advantages of the present invention have been more particularly described in connection with series connected windings of the motor of the system described, corresponding advantages are securable through utilization of the invention in connection with the commutating winding of the generator 12 of the system and a series winding which, instead of demagnetizing the generator field on increased motor load, proportionately increases the effective field energization of the generator to thereby automatically increase the voltage at the terminals of the latter and applied to the motor terminals as the load thereon increases, thereby prevening the speed of the motor from drooping.

Through the use of the present invention,

described herein, for obvious modifications within the scope of the appended claims will be apparent to persons skilled in the art.

It is claimed and desired to secure by Letters Patent:

1. A direct current dynamo-electric machine having a plurality of field energizing windings carrying current varying as the armature current of said machine, one of said windings exerting its energizing effects on the main field of said machine, another of said windings exerting its energizing eifects upon the commutating field of said machine, and said windings being connected in shunt to one another.

2. A direct current dynamo-electric machine having a pliu'ality of field energizing windings carrying current varying as the armature current of said machine, one of said windings exerting its energizing effects on the main field of said machine, another of said windings exerting its energizing effects upon the commutating field of said machine, and said windings being connected in shunt to one another, controlling means for varying a characteristic of the operation of said machine, and means operatively dependent upon said controlling means for varying the proportionate distribution of current in said windings.

3. A direct current dynamo-electric machine having a plurality of field energizing windings carrying current varying as the armature current of said machine, one of said wind'ngs exerting a demagnetizing effect on the main field of said machine proportionate to the armature current thereof, another of said windings exerting its energizing effects upon the commutating field of said machine, and said windings be ing connected in shunt to one another.

4. A dynamo-electric machine having a plurality of field energizing windings carrying current varying as the armature current of said machine and each exerting energizing effects different from that of the other in the operation of said machine, one of said windings exerting an automatic regulating effect on the main field of said machine which is proportionate to the armature current thereof, and said windings being connected in shunt to one another.

5. A direct current motor having a plurality of field energizing windings carrying current varying as the armature current of said motor, one of said windings exerting an increased demagnetizing effect on the main field of said motor as the load on said motor increases, another of said windings exerting its energizing effects upon the cornmutating field of said motor, and said windings being connected in shunt to one another.

6. A direct current motor having a plurality of field energizing windings carrying current varying as the armature current of said motor, one of said windings exerting its energizing effects on the main field of said motor, another of said windings exerting its energizing effects upon the commutating field of said motor, and said windings being connected in shunt to one another, and means for varying the proportional distribution of current in said windings.

7. A direct current motor having means for varying the effective potential at the terminals thereof, a plurality of field energizing windings carrying current varying as the armature current of said motor, one of said windings exerting its energizing effects on the main field of said motor, another of said windings exerting its energizing effects upon an auxiliary field of said motor, and said two windings being connected in shunt to one another, and means operatively dependent upon said potential varying means for varying the proportionate energizing effects of said field windings carrying current varying as the armature current of said motor.

8. A direct current dynamo-electric machine having a main field energizing winding, a plurality of auxiliary field energizing windings carrying current responsive to the armature current of said machine and each exerting an energizing effect different from that of the other in the operation of said machine, one of said field windings exerting a variable magnetizing effect upon the main field of said machine which varies as said armature current, and said auxiliary field windings being connected in shunt to one another, means for varying the current in said main field :inding, and means operatively dependent upon said current varying means for causing variation in the current in said auxiliary field Winding which exerts a magnetizing effect on the main field of said machine.

9. In a direct current system of power distribution, a motor, a generator connected to supply energy to the armature of said motor, one of said machines comprising a plurality of field windings carrying current varying with the current in the armature circuit of said machine and each exerting an energizing efiect different from the other in the operation of said machine, one of said windings exert-ing its energizing efiect on the main field of said machine and being effective to reduce the tendency of the speed of said motor to droop on increase in the load on said motor, said windings being connected in shunt to one another.

10. In a direct current system of power distribution, a motor, a generator connected to supply energy to the armature of said motor, one of said machines comprising a plurality of field windings carrying current varying with the current in the armature circuit of said machine, one

of said windings exerting its energizing effect on the main field of said machine and being effective to reduce the tendency of the speed of said motor to decrease on increase in the load on the motor, and another of said windings exerting its energizing effect on the commutating field of said machine, said windings being connected in shunt to one another.

11. In a direct current system of power distribution, a motor, a generator connected to supply energy to the armature of said motor, one of said machines comprising a plurality of field windings carrying current varying with the current in the armature circuit of said machine, one of said windings exerting its energizing effect on the commutating field of said machine, another of said windings exerting its energizing effect on the main field of said machine and being effective to reduce the tendency of the speed of said motor to decrease with increase in load thereon, and said windings being connected in shunt to one another.

12. In a direct current system of power distribution, a motor, a generator connected to supply energy to the armature of said motor, one of said machines comprising a plurality of field windings carrying current varying with the cur- 1' rent in the armature circuit of said machine and each exerting an energizing effect different from that of the other in the operation of said machine, one of said windings exerting its energizing effect on the main field of said machine and being effective to modify the tendency of the speed of said motor to vary with variation in the load on the motor, and said windings being connected in shunt to one another, means for adjusting the speed of said motor to desired values, and means operatively dependent upon said speed-adjusting means for varying the effect of said field winding acting on the main field of said machine.

13. In a control system, a direct current dynamo-electric machine having a plurality of field energizing windings carrying current varying as the current in the armature circuit of the machine, one of said windings exerting its energizing effects on the main field of said machine, another of said windings exerting its energizing effects upon an auxiliary field of said machine, and said two windings being connected in shunt to one another, means for varying the effective potential at the terminals of said machine, and

means operatively dependent upon said potential varying means for varying the proportionate energizing effects of said field windings carrying current varying as the armature current of said machine.

14. An electrical system comprising a direct current dynamo-electric machine having a plurality of field energizing windings carrying current varying as the armature current of said machine, one of said windings exerting a demagnetizing effect on the main field of said machine proportionate to the armature current thereof, another of said windings exerting its energizing effects upon the commutating field of said machine, and said windings being connected in shunt to one another, and means for varying the proportionate distribution of current in the said windings.

WILLIAM H. POWELL. 

